This invention relates to thermal pack devices, in general, and more particularly to a thermal pack utilized for warming the heel of an infant prior to obtaining a blood sample from the infant.
The field of thermal packs as those which produce heat or cold upon selective operation is replete with a large number of patents. Essentially, there are numerous types of thermal packs which are readily available according to such prior art techniques. Such packs exist in the marketplace and are sold by many companies. The typical thermal pack employs a sealed rectangular or other shaped package containing selected chemical ingredients which when finally intermixed together, provide either a refrigerated pack or a heated pack. As indicated, there are numerous examples in the prior art showing such techniques. References is made, for example, to U.S. Pat. No. 4,057,047 issued on Nov. 8, 1977 to R. L. Gossett and entitled MAGNESIUM SULFATE ANHYDROUS HOT PACK HAVING AN INNER BAG PROVIDED WITH A PERFORATED SEAL. See also U.S. Pat. No. 4,856,651 entitled CHEMICAL THERMAL PACK AND METHOD OF MAKING THE SAME to S. E. Francis, Jr. issued on Aug. 15, 1989. See also U.S. Pat. No. 4,580,547 entitled FLEXIBLE HEAT PACK CONTAINING SUPERCOOLED SALT SOLUTION by Kapralis et al. issued on Apr. 8, 1986.
Each of these thermal packs incorporate trigger mechanisms whereby when triggered, a heat or cooling reaction will take place. For such operations one can refer to other references such as U.S. Pat. No. 2,925,719 to A. A. Robbins wherein a refrigerating pack is provided containing a refrigerating chemical such as ammonium nitrate for reaction with water when an inner envelope is broken. The concept of enveloping one package within the other is well known in the prior art. See, for example, U.S. Pat. No. 2,907,173 issued to A. A. Robbins as well as U.S. Pat. No. 4,057,047 which shows a thermal reaction package utilized as a thermal pack whereby one compartment contains a quantity of urea while the other compartment is intended to be filled with water to create an endothermic or cooling reaction when mixed with the urea. As indicated, there is a plethora of patents in the prior art which teach the use of all types of chemicals which can be employed to operate in a thermal heated or refrigerated pack and which require the activation of a trigger to actuate the reaction to produce the effect. Reference is again made to the above-noted patent, U.S. Pat. No. 4,580,547 where a trigger is located in a container and when the trigger is deformed, chemical crystallization is initiated to produce heat. The trigger may comprise a thin, bendable metallic strip which can be activated when the trigger is in any position. The trigger which is located in the container is adapted to be deformed to initiate exothermic crystallization of a salt which is in a solution. The number of salts which store heat as the heat of fusion and which release heat upon crystallization are numerous. See, for example, U.S. Pat. No. 3,536,058 issued on Oct. 16, 1970 to Hearst et al. and entitled CHEMICAL HEAT BARRIER FOR WETSUITS. This patent describes many such salts, typical examples being sodium sulfate decahydrate, disodium phosphate dodecahydrate, as well as lithium nitrate trihydrate. Furthermore, it is well known to utilize mixtures of hydrated salts in supercooled liquid form to produce controlled eutectic temperatures of crystallization. There are virtually numerous salts which when activated by a trigger such as a suitable metal or other substance, will crystalize to produce heat. Basically such salts and materials may be referred to as temperature altering chemicals.
Thus, as one will appreciate, the above-noted patents and a host of other patents as well, describe various packages for applying heat or cold to applicable parts or areas of the body when activated or otherwise employed to keep a person or user warm under adverse ambient conditions. In this particular application, there is disclosed a thermal pack of a unique configuration which is intended to be used on an infant and to generate heat at a controlled temperature which allows the heel of the infant and its surrounding tissue as, for example, the leg and foot, to be elevated to a temperature of about 42.degree. C. In this manner the thermal pack will enable the blood vessels to dilate and thereafter a medical practitioner can puncture the heel of the infant to obtain a blood sample with a better blood flow because of the heated expanded blood vessels. Also, in the event that the sample is taken for the purpose of doing a blood gas analysis, it is necessary that the infant's foot be pre-warmed and the vessels be pre-warmed before the sample is taken. Generally speaking, it is required by legislation that every neonate have blood tests performed. Thus, every infant that is born in the United States has a blood sample drawn from a puncture usually made in the heel of the infant. These procedures utilize an instrument for making such incisions such as the TENDERFOOT instrument marketed and sold by the assignee herein.
Thus, it is an intent of the present application to provide a thermal pack which is particularly adapted for the above-noted use.
It is a further objective to provide a thermal pack of a unique configuration which can be triggered when use is desired and upon triggering, produces a phase transition from a supercooled liquid to a crystalline form and to emit a controlled heat.
As will be described, the thermal pack according to this invention is extremely easy to utilize and it is symmetrical so that it can be used by right or left handed persons with extreme ease and simplicity. The thermal pack is of a unique configuration to enable the heating of the heel of an infant to accommodate the required blood sampling.